Physics Lab – Virtual Ripple Tank (Informal Lab – Just fill in blanks)

Setup. a. Launch Mozilla Firefox b. Go to http://phet.colorado.edu/en/simulations/category/new c. Click on Physics on the left panel d. Click on “Sound & Waves” on menu that now appears (still on left) e. Click on “Wave Interference” f. Run Now! (if it asks you to update, just hit later)

WHILE THIS IS SETTING UP, READ THROUGH YOUR NOTES ON WAVE INTERFERENCE, REFLECTION, REFRACTION, AND DIFFRACITON.

Part 1: Investigate Ripple Patterns.

1. Play With The Ripple Tank – Observe the different ripple patterns you get with changes to the waves and the ripple tank. Write your observations below.

See what happens with one faucet vs two faucets.

Turn the faucets on and off.

Change the frequency and amplitude of the drops.

Add a barrier with one slit or two slits and move the barrier left and right.

Change the width and spacing of the slits in the barrier.

(continued on back) 2. Create An Interesting Ripple Pattern – Set the frequency near the middle of the scale. Set the amplitude near the right end (the high end) of the scale. Add a barrier (single slit) and put it at 6.2 cm (check the “Barrier Location” scale). Set the slit width to 2.5 cm or higher.

You may choose the other variables as you like – one faucet or two, one slit or two, any faucet spacing, any slit separation, etc. But be careful, because the next step is…

Make Some Observations:

3. Draw Your Ripple Pattern – Pause the ripple tank. Using a colored pencil for the crests and a dark pencil for the troughs, draw the ripple. Pay attention to where the colors are brightest and where they are dim. Be as exact as possible. If you would rather copy and paste the diagram using print screen, that is fine but you will need to label the crests and troughs of the ripple pattern. Part 2: Identify wave behaviors.

4. Reflection – Circle an area of your diagram above that shows wave reflection and label this area “reflection”.

5. Diffraction – Circle an area of your diagram above that shows wave diffraction and label this area “diffraction”. Below, describe what “diffraction” means.

6. Constructive Interference – Mark a point on your diagram above that is an example of constructive interference. Below, describe what “constructive interference” means.

7. Destructive Interference – Mark a point on your diagram above that is an example of destructive interference. Below, describe what “destructive interference” means.

8. Describe what is just beyond the right-hand side of the ripple tank and support your hypothesis using key terms from the Waves Unit. Part 3: Sound Waves

1. Using one speaker, what happens when you change the frequency of the pulse (look at the speaker and the waves)? Why?

2. Using one speaker, what happens when you change the amplitude of the pulse? Why?

3. Add a second speaker. What happens? Why?

4. Draw (or printscreen) this image and label the parts where there is interference. What type of interference is this? Label.

5. Turn off one of the speakers (but do not remove it). What happens? Explain. Part 4: Light Waves

1. Add 2 slit barriers to the light waves applet. What happens to the waves?

2. Draw (or printscreen) the diagram (you can press pause). Label the area where diffraction occurs. Label the area where reflection occurs. Label where there is constructive interference and destructive interference.

3. What happens if you make the slit separation larger? What happens if you make the slit separation smaller? Why?

4. Get rid of your slits. Add a mirror in. What happens to the waves now?

5. If you make the mirror smaller, what happens in terms of diffraction? (To do this, click on one of the circles on the mirror and drag the mirror to be smaller). 6. If you change the angle of the mirror, what happens in terms of reflection? (To do this, click on one of the circles on the mirror and drag the mirror to move one end).